Kung Fu Fighting(15) - Inflict a set amount of damage to Wesker in "Lost in Nightmares."
Must've Got Lost(15) - Complete "Lost in Nightmares" on any difficulty setting.
Wish Upon a Star(15) - Destroy all 18 of the Score stars found throughout "Lost in Nightmares."
It's Just a Bad Dream(15) - Complete "Lost in Nightmares" with an S rank.
Night Terrors(40) - Complete "Lost in Nightmares" on Professional.

Additionally, there are ten Versus DLC achievements:

Eye of the Tiger (15) - Win 30 matches in Survivors.
It Takes Two to Tango (15) - Chain a 40-defeated combo in Team Slayers.
It's All About the Points (15) - Score at least 40,000 points in Survivors.
Army of One (15) - Win 30 matches in Slayers.
The Team That Slays Together... (30) - Win 30 matches in Team Slayers.
There's no "I" in Team (15) - Score at least 80,000 points in Team Survivors.
Bringing the Pain (30) - Defeat 100 players using physical attacks in Versus.
Keep the Good Times Rolling (15) - Chain a 20-defeated combo in Slayers.
Let's Get This Party Started! (20) - Unlock all selectable characters in Versus.
We Will Survive (30) - Win 30 matches in Team Survivors.

Additionally, there are five Desperate Escape DLC achievements:

Shoot the Messenger (15) - Defeat 3 Agitator Majini in one playthrough of "Desperate Excape."
Way of the Warrior (15) - Defeat 150 enemies singlehandedly in one playthrough of "Desperate Escape."
The Great Escape (15) - Complete "Desperate Escape" with an S rank.
Getaway (15) - Complete "Desperate Escape" on any difficulty setting.
Run the Gauntlet (40) - Complete "Desperate Escape" on Professional.

Regenerate Items (Chapter 2-1)
Take all the items at the beginning and then Quit the game. Return to the game by selecting "Continue" and you will begin Chapter 2-1 with the items you got before you quit the game, however, the items at the beginning (you took just now) are still at the same place, so you can obtain them again. Repeat the same thing to get as many as you like.

Unlimited Ammunition for a Single Weapon
Get all upgrades for a weapon to receive unlimited ammunition for it.

Shanty Town: Staying Together
Go up to the building that has two frag grenades. You can go off of the edge and bounce them off of the sign named "KENNYS". If done correctly, this will blow off the lock, eliminating the need for Sheva and yourself to be separated.

Unlimited Money
At the beginning of Chapter 2-1, you will be in a garage with two Humvees, numerous breakable crates, and a machine gun. Pick up any items you wish, including the machine gun. End the game, and select "Yes" to overwrite your current equipment. Continue the game from the main menu. You will have gained your items, as well as the machine gun. From here you can sell the machine gun back for quick money, then repeat the process over again. This is an easy way to help upgrade your weapons early, as well as max your ammo out.

Unlock Bonuses
Mercenaries Mode - Finish the game in any difficulty.
New Game+ - Finish the game in any difficulty.
Playing with Sheva - Finish the game in any difficulty.
Unlimited ammuntion for a weapon - Max out the upgrades for that gun.
History of Resident Evil - Beat the game on any difficulty.
Professional Difficulty - Beat every chapter on Veteran.

Unlock Mercenary Characters
Jill (Battle Suit) - Get an A Rank or higher in Ship Deck.
Jill (BSAA) - Get an A Rank or higher in Public Assembly.
Chris (Stars) - Get an A Rank or higher in Experimental Facility.
Chris (Safari) - Get an A Rank or higher in The Village.
Sheva (Tribal) - Get an A Rank or higher in Missile Area.
Sheva (Clubin) - Get an A Rank or higher in Ancient Ruins.
Wesker (Midnight) - Get an A Rank or higher in The Mines.
Wesker (STARS) - Get an A Rank or higher in The Prison.

Caves: Defeating the Boss
When you face the flying bat/insect-like creature for the second time in Chapter 4-1, there is an easy way to defeat him which will allow you to still get the Soul Gem. In the southwest corner of the bottom floor, there is a small pillar of stone in the middle, with what looks to be a log with spikes coming out of it as well as a rib cage hanging from it. When Sheva tells you that it is too hard to fight and you should go upstairs, if done correctly you can just walk backwards without having to dodge around the pillar as the Boss tries to attack you. The "Dodge" button will appear, but it is not necessary. Just continue to walk backwards around the pillar and attack with whatever you have when it is vulnerable, shooting the soft portion on the back of its tail. When it dies you can collect the Soul Gem which is worth 10,000 gold when sold.

Public Assembly: VZ61 Machine Gun
After the gate has broken open, you can enter the market. Go all the way down the street until you see big red doors and gas cans next to them. Turn right just before the gas cans. There will be a brief case you can open with a VZ61 Machine gun in it. If you look closely, the gun looks similar to the "Scorpion" sub machine gun from Call Of Duty 4. This gun will make this level much easier.

Uroboros Research Facility: Easy Ammunition
In Chapter 5-2, "Uroboros Research Facility", after the conveyor belt area and you start a new checkpoint, you reach a point where you drop down. There are a number of crates with flame rounds, rifle rounds, handgun ammo, and an incendiary grenade. Collect everything, then save the game and quit. When you start again, remove the collected items from the item management screen and collect them all again. You can get 300 handgun bullets in a matter of ten minutes.

Mercenaries Mode: Getting Better Ammunition
The ammunition that drops is based on the type of weapons you have. Drop weapons that you will not use to increase the chance of getting ammunition that is more useful.

Mercenaries Mode: Quick Reload
Display the inventory screen and combine ammunition manually with your weapon. This causes weapons such as the shotgun to reload much faster than the normal method. You can also use this trick while climbing ladders or jumping.

Defeating Wesker
To quickly and safely defeat Wesker in his first form, run to all the levers around the map to turn the lights off. You do not need to go up the ladders because there are no levers up there. Do not worry about attacking him until you have turned off all the lights, otherwise you will not be able to hit him. After all the lights have been turned off, take the rocket launcher in the display case after breaking it open. Run to a dark corner far away from him. Wesker will look around to try and find you. When this happens, you will have a chance to shoot a rocket at him. As soon as you shoot it, he will grab it. Run up to him (or shoot the rocket in his hands), stun him, and initiate a button context. If you need more ammunition you can send Sheva to fetch it, or you can get it by climbing to the area above the ladders. The second form is nothing but a button context scene battle, and there is no specific strategy needed. In his final form, start by running to the high ground. Then when in the circular area, shoot the orange "heart" that alternates from his chest to his back while dodging his attacks. After he takes enough damage, he will go after Sheva. At this point, run down the ramp from the circular area you were just in. Make a left to arrive at a large boulder. Instead of interacting with the boulder just yet, shoot Wesker from afar, while Sheva hangs in the balance. Once she lifts herself up, start to move the boulder using the button contexts. Make your way back to the high ground and repeat the orange heart strategy until he has been defeated.

Use the following trick to defeating Wesker's Final Form. Once you have saved Sheva from Wesker and have pushed the boulder over to allow her to join you, you will once again be attacked by Wesker, when you run to the higher ground where you faced him earlier. Like before, dodge his attacks as you shoot his heart, which alternates between his chest and back. Once you do enough damage to his heart, he will kneel down and push his arm into the ground. It then comes up around him as many swirling tentacles, protecting him from fire. If you wait and do nothing after he gets back up, you will see a cinematic of tentacles recovering his heart, which you do not want to happen. To prevent this, as soon after the swirling tentacles recede, run up to him and there should be a button event will begin, allowing you to hold him while Sheva stabs him (and later you), which is how you can finally kill him.

Efficient Healing
If both players stand in front each other and one of them heals themselves, both persons will get healed.

Mercenaries Mode: Wesker's Dash Move
While playing as Wesker in Mercenaries mode, click the Right Analog-stick to dash. You can press [X] during a dash to do a knee attack.

Lost in Nightmares DLC: Play as Jill Valentine
Complete the game on any difficulty setting, you may choose to play a Jill on you next playthrough.